rails can't find database.yml

I just removed my database.yml because I'm trying to use Mongoid, and now I'm getting the following:

$ rails server           
=> Booting WEBrick
=> Rails 3.0.9 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
/usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/application/configuration.rb:88:in `read': No such file or directory - /home/chris-kun/code/thirsty/config/database.yml (Errno::ENOENT)
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/application/configuration.rb:88:in `database_configuration'
        from /usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.9/lib/active_record/railtie.rb:58:in `block (2 levels) in <class:Railtie>'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/lazy_load_hooks.rb:26:in `on_load'
        from /usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.9/lib/active_record/railtie.rb:57:in `block in <class:Railtie>'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/initializable.rb:25:in `instance_exec'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/initializable.rb:25:in `run'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/initializable.rb:50:in `block in run_initializers'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/initializable.rb:49:in `each'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/initializable.rb:49:in `run_initializers'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/application.rb:134:in `initialize!'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/application.rb:77:in `method_missing'
        from /home/chris-kun/code/thirsty/config/environment.rb:5:in `<top (required)>'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/dependencies.rb:239:in `require'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/dependencies.rb:239:in `block in require'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/act开发者_如何学Cive_support/dependencies.rb:225:in `block in load_dependency'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/dependencies.rb:596:in `new_constants_in'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/dependencies.rb:225:in `load_dependency'
        from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/dependencies.rb:239:in `require'
        from /home/chris-kun/code/thirsty/config.ru:3:in `block in <main>'
        from /usr/lib/ruby/gems/1.9.1/gems/rack-1.2.3/lib/rack/builder.rb:46:in `instance_eval'
        from /usr/lib/ruby/gems/1.9.1/gems/rack-1.2.3/lib/rack/builder.rb:46:in `initialize'
        from /home/chris-kun/code/thirsty/config.ru:1:in `new'
        from /home/chris-kun/code/thirsty/config.ru:1:in `<main>'
        from /usr/lib/ruby/gems/1.9.1/gems/rack-1.2.3/lib/rack/builder.rb:35:in `eval'
        from /usr/lib/ruby/gems/1.9.1/gems/rack-1.2.3/lib/rack/builder.rb:35:in `parse_file'
        from /usr/lib/ruby/gems/1.9.1/gems/rack-1.2.3/lib/rack/server.rb:162:in `app'
        from /usr/lib/ruby/gems/1.9.1/gems/rack-1.2.3/lib/rack/server.rb:253:in `wrapped_app'
  1 #!/usr/bin/env ruby
        from /usr/lib/ruby/gems/1.9.1/gems/rack-1.2.3/lib/rack/server.rb:204:in `start'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/commands/server.rb:65:in `start'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/commands.rb:30:in `block in <top (required)>'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/commands.rb:27:in `tap'
        from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/commands.rb:27:in `<top (required)>'
        from script/rails:6:in `require'
        from script/rails:6:in `<main>'

Any ideas?

In config/application.rb, remove the line require 'rails/all' and replace with:

require "rails"

%w(
  action_controller
  action_mailer
  active_resource
  rails/test_unit
).each do |framework|
  begin
    require "#{framework}/railtie"
  rescue LoadError
  end
end

(This is the contents of rails/all.rb in the railties gem, but with the activerecord line removed).

I had a similair issue before, but it turns out I had some scattered active_record references lying around. Full credit to Dylan Markow for this one!

Removing database.yml when using Mongoid in Rails 3.2

Execute grep -r active_record config/ to find all references, then comment them out!

For those of you who want to use db related functions ex) rake db:seed with mongoid, also add the mongoid railtie:

https://github.com/mongodb/mongoid/tree/master/lib/mongoid/railties

require "rails"

# Import gems in Gemfile
Bundler.require(*Rails.groups)

# important that this is imported after gems in Gemfile are imported
%w(
  mongoid
  action_controller
  action_mailer
  active_resource
  rails/test_unit
).each do |framework|
begin
  require "#{framework}/railtie"
    rescue LoadError
  end
end

An updated answer for Rails 5 and all future versions of Rails:

You should be using the require snippet from the rails/all.rb file that is current with your version of Rails without the active_record railtie. Here is a link to rails/all.rb on the Rails master branch.

As of writing this it includes a number of new railties which you don't want to miss out on:

require "rails"

%w(
  action_controller/railtie
  action_view/railtie
  action_mailer/railtie
  active_job/railtie
  action_cable/engine
  rails/test_unit/railtie
  sprockets/railtie
).each do |railtie|
  begin
    require railtie
  rescue LoadError
  end
end